Conventionally, an optical switch is known that interrupts or transmits an optical beam from an optical waveguide by moving a screen plate placed halfway through the optical waveguide as a configuration of an optical switch. Japanese patent application laid-open Nos. 05-257069(1993) and 02-131210 (1990) disclose concrete configurations of such an optical switch. In the following description, the optical switch with a configuration disclosed in Japanese patent application laid-open No. 05-257069 (1993) is referred to as a conventional technique A, and the optical switch with a configuration disclosed in Japanese patent application laid-open No. 02-131210 (1990) is referred to as a conventional technique B to explain the conventional techniques.
FIG. 9 is a plan view illustrating a configuration of the optical switch disclosed as the conventional technique A. The optical switch includes a glass piece 115 movable along a groove provided in an interior 113 of a groove section 112 crossing an optical waveguide 111 formed on a substrate; a liquid metal holding groove 117 placed at both ends of the glass piece 115 and communicating to the groove section 112, for holding a liquid metal (mercury) 116 in the interior; electrodes 118A, 118B and 119A, 119B for flowing current through each of the liquid metals 116 held in the interior of the liquid metal holding groove 117; and a magnetic field applying section (not shown) for applying a magnetic field in a direction perpendicular to the current direction.
Then the glass piece is moved in such a manner that a metal mirror 114 mounted on a part of the glass piece interrupts the optical waveguide 111 by applying a magnetic field in a direction (Z direction) perpendicular to a direction (X direction), in which a current flows when the current is supplied across the liquid metal 116, so that the liquid metal 116 experiences the Lorentz force and is moved in the Y direction through the liquid holding groove. In contrast, an input light passing through the optical waveguide 111 is transmitted by removing the metal mirror 114 from the optical waveguide 111 by reversing the direction of the current. By thus controlling the direction of the current flowing through the liquid metal 116, the light propagating through the optical waveguide 111 is interrupted or transmitted, thereby implementing the optical switch. As for the optical switch with the configuration, magnets (not shown) are placed at the upper and lower sides of a substrate to generate the magnetic field in the direction (Z direction) perpendicular to the substrate.
FIG. 10 is a schematic cross-sectional view showing a configuration of an optical switch disclosed as the conventional technique B. In FIG. 10, the reference numeral 121 designates a displacement plate composed of a conductive material, 122 designates an element at the front end of the displacement plate 121 for interrupting/transmitting propagating light, 124 designates an insulating layer for supporting the rear end side of the displacement plate 121, 125 designates a switch, 126 designates a power supply, 128 designates an optical waveguide, 127 designates a gap across the optical waveguide 128, and 123 designates a conductive material layer mounted on a surface of the optical waveguide 128 in such a manner that the conductive material layer is parallel to the waveguide direction of the light.
In the optical switch with the configuration as shown in FIG. 10, the element 122 moves in a direction normal to the substrate (up and down direction of the sheet) because of the electrostatic force caused between the displacement plate 121 and the conductive material layer 123 by applying voltage, thereby carrying out the optical switch operation of interrupting/transmitting.
As for the optical switch configuration of the conventional technique A, it requires a space for placing in the optical waveguide the driving section composed of the liquid metal holding groove and electrodes for operating the moving section. Accordingly, upsizing of the optical switch including the driving section as its integral part is unavoidable. In particular, the space for the driving section has a problem of hampering the high-density integration of the optical switch elements, when the optical switch elements are placed in a matrix on the same substrate.
On the other hand, the optical switch configuration of the conventional technique B has the screen plate moved in the direction perpendicular to the substrate, and has the structure that accesses the optical waveguide from the upper side of the optical waveguide. Thus, it is not necessary for the optical switch to have a driving mechanism within the optical waveguide. In this respect, the optical switch can be considered to have the configuration suitable for high-density integration of the optical waveguide. However, since the configuration utilizes the electrostatic force as the driving force, it requires a high voltage for driving, and hence upsizes peripheral electronic circuits and devices, thereby limiting the downsizing of the optical switch as a whole.
Therefore a driving system that enables both the “Lorentz force driving” and “vertical movement of the moving section”, which are the technical advantages of the foregoing configurations, will be able to implement the high-density integration of the optical waveguide and the downsizing of the device at the same time. A configuration of such an optical switch (optical device), however, has not yet been known.